1. Field of the Invention
The present invention relates generally to the operation of automated or robotic assembly equipment, especially for the manufacturing of windows, and in particular to any such equipment adapted for pickup of sheets, panels, films, webs or laminates of various sizes at a first location and the placement or attachment of such material at a desired second location, such as to frames of multi-pane insulating glass units (IGUs).
2. Description of the Related Art
As the cost of fossil fuels and other energy sources continues to rise and people become more concerned with the impact that energy generation has on the environment, there has been an increased interest in energy conservation. Products which themselves are not responsible for energy consumption, but which have an effect on the energy consumption of other devices, are in increased demand.
In architectural structures, generally the most energy demanding activity is climate control. Whether cooling or heating, the desire to maintain the interior temperature of a structure at a temperature comfortable for the average human in standard attire can be very energy intensive. While, in some climates, the outside temperature is commonly within a desirable range and climate control is inexpensive and not heavily used, in most environments, at least for a portion of the year, there is a desire to alter the environment within a structure compared to the environment outside. In some environments, the temperature differential between the inside of a structure and the outside environment can be large with differences in temperature of 20° C. or more.
One of the best ways to both control the energy expended to alter the temperature and to maintain a temperature in a structure is to properly insulate the structure. While not an active technology in most cases, insulation allows for the temperature differential inside and outside the structure to be maintained without as much infusion of energy. Good insulation is a barrier to heat transfer. Thus, less energy is required to maintain the temperature, and the temperature is more easily maintained in a particular range.
The science of insulated glass is well understood, and it is critical in high-performance building envelopes. The current state of the art is the use of multi-pane windows. These windows utilize multiple panes of glass, which are separated by air gaps, to provide for insulating structures without sacrificing transparency. The windows generally improve their insulating capacity through the simple addition of more glass panes. Double-pane windows provide good insulation while triple- or even quadruple-pane windows provide additional insulation. This technology can be combined with certain types of coatings for the panes to provide for additional spectral manipulation including near-infrared reflection or transmission or thermal radiation characteristics. While these products work very well from an insulation perspective, they suffer from a couple of major drawbacks.
Using more than two panes of glass in a window makes the window significantly thicker and heavier. This can make the windows more expensive to manufacture and to transport as well as making them unusable for some types of applications, such as large office towers. Thus, while double-pane windows have become near ubiquitous, triple-pane windows are rare and quadruple-pane windows are almost unheard of.
In order to deal with these concerns U.S. Pat. No. 4,335,166 to Lizardo et al describes a thermally insulating multi-pane glazing structure, known in the industry as an insulating glass unit or IGU, in which the interior pane is an interior glazing sheet such as a polyethylene terephthalate (PET) film. This film is suspended between outer, generally glass, panes and separated therefrom by spacers, and one embodiment describes the use of a heat-shrinkable film. This provides the structure of a triple-pane (or more) window while dramatically reducing the weight of the center pane(s) and, thus, the window's weight and thickness.
In order to assemble such a structure, it has generally been necessary to take the exterior panes, which are usually rigid, attach spacer frames around the interior periphery of the panes with an adhesive, and suspend the PET film between the two spacer rings. A primary sealant such as polyisobutylene (PIB) may be placed between the film and the spacer as well as between the spacer and the glass to enhance durability and act as an assembly aid. PIB is tacky and can, therefore, temporarily fasten the film or glass to the spacer. A sealant is peripherally applied around the spacer frame to mechanically anchor the film, spacer frames, and glass panes. The interpane voids are then preferably filled with a low heat transfer gas.
In order to provide for the aesthetics of a glass-like window structure when utilizing such an internal film and to maintain a prescribed cavity spacing, it is necessary for the film to be taut over the spacers. A taut film will generally not include wrinkles or waves. However, applying the film so that it is taut during assembly to the spacers and keeping it taut is generally impossible. In order to get the film in place and taut, the film is generally placed in a reasonably taut fashion, secured by the spacer and cured sealant system, and then thermally shrunk in place by heating the IGU. The heat makes the film taut. However, for the thermal shrinking to work well, the film still needs to be relatively flat in the IGU to begin with.
Due to the lack of standard window sizes, IGUs are often custom made and largely constructed by hand. Any flexible film sheet must be cut to the required size and then carefully attached to the spacer frame. Currently, this is done by hand as the film can be difficult to handle and, since it is being attached to an adhesive, a missed positioning can result in a damaged product or a fold or wrinkle that cannot be easily removed and that thermal shrinking cannot correct. Further, since each piece of film can be different, and cut from a different position from an unrolling roll of film, there is no standardization from one IGU to the next in construction making the process difficult for automation.